Tire size question

[007CobaltLS]

I'm not saying they don't fit, I'm not questioning anyone, etc. I just came across this thread a few days ago and thought I would share.

Moral of the story..even if they appear to fit..double check or have a tire shop make sure they're fitting correctly.

Warning about ASA Wheels. - LS1TECH

Disclaimer: I know he's talking about ASA wheels (that's how I found it...was looking for more info on ASA's since I am interested in the GT06's)...but thought it was interesting to read. I also know he has a Monte SS...but the fact is any aftermarket wheel and any car should be checked to make absolute sure they're fitting just right.

 

[Eric Smit]

interesting.


-Eric Smit

 

[laborsmith]

In the early days of this site (it may not even had 100 members, that early) I posted my version of advice based on my experiences buying after market wheels and tires. To repeat myself, my advice is to buy from a local reseller so you can have tires and wheels test fitted. I have experienced needing to go to a less wide tire because of rubbing and to a different rim because of caliper clearance and it is just easier if you can stand beside the installer when there is a problem.

My other recommendation is if you buy a new set of rims and think you might be keeping them for a while, go ahead and spring for a fifth rim. Tuner rims are style items (not talking about performance rims such as Forgeline etc. which start at $1000 each) and some rims will go in and out of production and some will be produced for a while then never produced again.

That is my two cents on the subject.


Laborsmith

 

[Eric Smit]

on that note, which I remember reading over a year ago, I wonder if a normal size wheel will fit in the spare tire well. or rather, can be made to fit.


-Eric Smit

 

[american_tuner]

Thinking im gonna go with the sparco 18 x8. Been looking at some tires of 225/40 or should i go with a 35 series?

 

[Eric Smit]

35 will be gross. so will 215.


-Eric Smit

 

[american_tuner]

I wouldn't mind going 245 but afraid it would rub especially when my springs eventually come in lol

 

[rdss]

A little late to the game, but I'm running 225/45/17's on the 6.5" LTZ wheels and the look great. The 7" wide wheel will only make it look better. Fitment is going to be one of the other guys, I have Preload's take off spacers coming in the mail to push the stock LTZ's out kinda flush.

 

[Eric Smit]

I'd get 235/40.


-Eric Smit

 

[laborsmith]

I wouldn't mind going 245 but afraid it would rub especially when my springs eventually come in lol

Altho I did not try 235s, we talked about it and after putting the mounted 225 on, I determined a 235 would likely rub and that was before lowering. I do not see a 245 fitting w/o a custom offset, but there is only one way to find out. What that way is eludes me, but I am sure you can figure it out.

Laborsmith

 

[american_tuner]

Laborsmith

I have decided to go with 17 and gonna go with a 235. My question here is what kind of big difference would there be in a 40 offset vs a 42

 

[Eric Smit]

2 mm.


-Eric Smit

 

[laborsmith]

Laborsmith

I have decided to go with 17 and gonna go with a 235. My question here is what kind of big difference would there be in a 40 offset vs a 42

Here is what I use: Wheel Offset Calculator

A 225 will be about 8.9" (tire brands have slight variations) so a 235 would be about 9.3". In addition, the wheel width makes an even more significant difference, as you will discover when you use the calculator.

If you want to be perfectly flush you will almost need to use trial and error. As a guide my 225 tire on a 7.5" .40et wheel is the depth of a wooden ruler away from flush, or about .25 inches. Visually the tires come very close to the suspension, both front and back. I myself would not try 235 unless someone else has with no reports of rubbing. Of course both the LT and now the RS are lowered, if that makes a difference in your thinking.


Laborsmith

 

[american_tuner]

Here is what I use: Wheel Offset Calculator

A 225 will be about 8.9" (tire brands have slight variations) so a 235 would be about 9.3". In addition, the wheel width makes an even more significant difference, as you will discover when you use the calculator.

If you want to be perfectly flush you will almost need to use trial and error. As a guide my 225 tire on a 7.5" .40et wheel is the depth of a wooden ruler away from flush, or about .25 inches. Visually the tires come very close to the suspension, both front and back. I myself would not try 235 unless someone else has with no reports of rubbing. Of course both the LT and now the RS are lowered, if that makes a difference in your thinking.


Laborsmith

You said the 225 you have comes very close to the suspension, how close would it be? Like paper thin close?

 

[laborsmith]

Way more than paper thin, maybe a quarter inchish. Certainly not as much as a half inch. I think 235 might work and I can't see an installer even trying a 245, but if you find one who will and it works that would be awesome.

Laborsmith

 

[Preloader]

215's + 7.5W wheels + 42mm offset + 2.5" drop on my car = 1/8" clearance between inner tire wall and lock nuts of coilover.

 

[american_tuner]

215's + 7.5W wheels + 42mm offset + 2.5" drop on my car = 1/8" clearance between inner tire wall and lock nuts of coilover.

So if i went with a 40mm it would hive me a bit more room?

 

[Preloader]

If you are using all things the same but the offset, you will end up with 2mm more room than what I have.

All things the same meaning severe drop on Pedders coilovers, and 215's on 7.5" wide wheels.

 

[laborsmith]

I sense you are wanting the widest possible setup. With that in mind perhaps first install the lowering system of choice. My memory is based on my LT with the Pedders lowering coils which provide a milder drop then coil overs could.

Another thing you might consider: staggered tires, say 225 in front and 235 in back on the same size wheels. I suggest same size wheels because I am not a fan of different sized front and rear on non sport cars although that does work well on Vettes and similar cars.

I would not go wider than 225 on the front even if it would fit because the wider you go the more stress you put on the steering system.

Finally, I think you need to find an installer willing to test fit. Rims are pretty consistent in measurements but tires are not. People might be amazed to see the difference when two tires of the same size but different brands are put together side to side.


Laborsmith

 

[american_tuner]

Laborsmith and preloadet,

Thank you for the insight and will follow your recommendations. Ive been stressing out about tire size and offsets lol. To get a flush it seems ill have to get spacers or custom wheels. No custom over here. So spacers will probably follow. Thanks again for all of the help.